Soil additives may be used to improve soil quality in these areas as well as broader agriculture applications. For years, soils have been studied to determine which types of soils are best suited to grow which types of plants. From this analysis, it has been determined that different types of crops and other plants grow best in certain types of soils. In order to prepare a plot of soil to have the desired plant supporting features, soil amendments are formulated and added to soils. A wide variety of materials have been used in various mixtures to attempt to achieve these desired results.
Additives have been mixed with soil to assist the soil in performing a variety of functions including retaining water and moisture, elevating soil temperature, controlling weeds, adding nutrients, allowing water to drain from the soil, controlling pests such as insects, bacteria and fungi, and other functions that are required for or conducive to supporting plant growth. The amount of these materials that are to be added to the soil is determined by a combination of the amount of the types of plants to be raised, the desired characteristics of the soil, and the existing characteristics of the soil prior to the addition of any amendments.
One way of amending the soil to improve soil conditions is to use a chemical fertilizer application. Such chemical fertilizer applications are available in a variety of forms. One of the most common forms being a spray wherein the fertilizer is suspended in a liquid and then applied to plants or soils. The addition of commercial fertilizers to a soil while providing the soil with an increased amount of one or several nutrients also depletes the soil of other nutrients and minerals. Over time, the composition of the soil becomes depleted and additional amendments to the soil are required. As a result, plants utilizing the chemical fertilizer deplete the soil of other resources and become stagnated, therefore unable to achieve their full potential. Another negative aspect of chemical fertilizers, and other man-made chemical compositions is that many times these are made of petroleum and other chemical based products that deplete natural resources and place unnatural and non-biodegradable materials into the soil.
Optimizing the sulphur nutrition of crops is a key to achieving crop yield and quality. Progress has been made in the last few decades in identifying the nature and cause of sulphur deficiency in soils and in the creation of sulphur-based fertilizers or soil amendments. Some background is necessary on the relationship between sulphur types, their creation and the relationship to plant growth.
Sulphur, the tenth most abundant element in the universe, and is a component of many common minerals, such as galena (PbS), gypsum (CaSO4.2(H2O), pyrite (FeS2), sphalerite (ZnS or FeS), cinnabar (HgS), stibnite (Sb2S3), epsomite (MgSO4.7(H2O)), celestite (SrSO4) and barite (BaSO4). Nearly 25% of the sulphur produced today is recovered from petroleum refining operations and as a byproduct of extracting other materials from sulphur containing ores. The majority of the sulphur produced today is obtained from the processing of sour gas, usually found in conjunction with salt deposits, with a process known as the Frasch process. The Frasch process has proven too costly and when compared with more conventional processes.
Sulphur is a pale yellow, odorless and brittle material. Most of the sulphur that is produced is used in the manufacture of sulphuric acid (H2SO4). Large amounts of sulphuric acid, nearly 40 million tons, are used each year to make fertilizers, lead-acid batteries, and in many industrial processes.
Elemental sulphur (S0) is a hydrophobic, insoluble particle that is dependent on microbial colonization of its surface and subsequent oxidation in order to be useable to plants. In other words, the primary form of sulphur that plants absorb through roots is in the sulphate form (SO4). Elemental sulphur (or other types of inorganic sulphurs) is thus rendered “plant available” by oxidation to sulphates (for example calcium sulphate, potassium sulphate, ammonium sulphate).
The oxidation of So to SO4 in soil is a biological process and is carried out by several kinds of microorganisms. The rate at which this conversion takes place is determined by three main factors: 1) the microbiological population of the soil; 2) the physical properties of the So source; and 3) the environmental conditions in the soil. Most agricultural soils contain some microorganisms that are able to oxidize So; however, the most important organisms in this respect are a group of bacteria belonging to the genus Thiobacillus. It is the numbers of these bacteria that generally determines the degree to which So is converted to SO4 in soils, and there can be large differences between soils in the population density of Thiobacillus. Under laboratory conditions, the rate of So oxidation in some soils can be markedly increased by inoculation with However, under field conditions, inoculation has not been found very effective. When a source of So is added to a soil, it generally stimulates the growth of S-oxidizing bacteria, and the population of these organisms increases.
The physical property that has by far the greatest effect on the rate of So oxidation is particle size. The finer the particle size, the larger the surface area exposed to soil microorganisms and the more rapid the oxidation process. Table 1 clearly shows this effect of particle size.
TABLE 1Particle Size Affects Rate Of S Oxidation.Particle Size% S Oxidized(Meshes/Inch)2 Weeks4 Weeks 5-101210-202520-4051440-801536 80-1203668 20-17061812308082
A mesh size of 5-15 is about the size range of bulk blended fertilizers and it can be seen that an S particle of this size is oxidized to SO4 very slowly. In order for So to be oxidized to the plant-available SO4 form at even moderate rates, it must be of a very fine particle size. But finely divided S is very difficult to handle, in addition to posing a fire hazard under some conditions. All this would seem to largely rule out the use of So as a fertilizer material.
Also, oxidation rates of elemental sulphur are slow in cold, dry soils and under other conditions which hinder the necessary oxidation process. This has led to considerable research in the area of enhancing this oxidation step by manipulating the particle size of elemental sulphur (there is faster oxidation the smaller the particle size).
Creation of micronized particles of elemental sulphur creates increased surface area for microbial colonization and hence oxidation. Fertilizer manufacturers have developed techniques to improve the handling characteristics and agronomic effectiveness of So. Elemental sulphur is first ground to a very small particle size range and is then agglomerated to a particle size compatible with granular fertilizer materials. About 10-15% of an expandable clay is added during the agglomeration process. The resulting material is theoretically more easily handled than finely divided S. In theory, when such a particle is applied to a soil, it comes in contact with soil moisture. As this moisture is absorbed by the particle, the clay expands, which in effect breaks the particle down into a much finer size range. Naturally, there are costs associated with these pre-oxidation processes and micronization.
It is an object of the present invention to obviate or mitigate all of the above-noted disadvantages.